Relastivistic reaction?

[eri3an]

Old stars gets there energy from the fusion of 3 helium cores to one carbon-12 core. The resting mass of one carbon-12 is 2,99805 times bigger then the helium core. How much energy do you i from 1kg of helium? how do I even attack this problem?

[Astronuc]

Fusion energy is derived from the nuclear binding energy.
http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/nucbin.html

Three alpha particles (2He4) can fuse to form a 6C12 nucleus.

The energy released is the difference in the rest energy of the products and reactants, and use E = mc2.

http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/fuscon.html

http://hyperphysics.phy-astr.gsu.edu/hbase/astro/helfus.html
http://hyperphysics.phy-astr.gsu.edu/hbase/astro/astfus.html

[HallsofIvy]

Old stars gets there energy from the fusion of 3 helium cores to one carbon-12 core. The resting mass of one carbon-12 is 2,99805 times bigger then the helium core. How much energy do you i from 1kg of helium? how do I even attack this problem?

Let m be the rest mass of one helium core. Then three helium cores have mass 3m but the resulting carbon-12 core has mass only 2.99805m. Energy has been released equivalent to (3- 2.99805)m= 0.00195m. Since that is for 3 helium cores, with 1 kg of helium, you can take the total m= 1/3 kg. Now use E= mc2.